Identification of a salt-induced primary transporter for glycine betaine in the methanogen Methanosarcina mazei Go1

The salt adaptation of the methanogenic archaeon Methanosarcina mazei G (o) double under dot1 was studied at the physiological and molecular levels. The freshwater organism M. mazei G (o) double under dot was able to adapt to salt concentrations up to I M, and the addition of the compatible solute glycine betaine to the growth medium facilitated adaptation to higher salt concentrations. Transport studies with cell suspensions revealed a salt-induced glycine betaine uptake activity in M. mazei G (o) double under dot1, and inhibitor studies argue for a primary transport device. Analysis of the genome of M. mazei G (o) double under dot1 identified a homolog of known primary glycine betainte transporters. This gene cluster was designated Ota (osmoprotectant transporter A). Its sequence and gene organization are very similar to those of the glycine betaine transporter OpuA of Bacillus subtilis. Northern blot analysis of otaC revealed a salt-dependent transcription of this gene. Ota is the first identified salt-induced transporter for compatible solutes in Archaea.